What happens when the defrost termination thermostat reaches its temperature limit?

When the defrost termination thermostat reaches its specified temperature limit, it indicates that the frost and ice buildup in the evaporator has been sufficiently melted away. This action is crucial to ensure proper operation of the refrigeration system and prevent overheating or further ice accumulation.

In this scenario, the correct function is that the thermostat sends a signal that activates the cooling cycle to resume normal refrigeration operation. It does this by supplying power to the release solenoid on the defrost timer, allowing the system to revert from defrost mode back to its regular cooling mode. This means that the refrigeration process can continue to keep the necessary temperatures for food preservation.

The other options involve actions that do not accurately describe the function of the defrost termination thermostat. For example, shutting off the entire system would stop all operations, which is not its purpose. Activating cooling directly without a signal from the thermostat does not reflect the process flow, as it is the thermostat that controls this transition. Lastly, switching on the heater is contrary to the role of the termination thermostat, which functions to signal that the heater should stop operating once the desired defrost temperature is achieved.